Games are played for entertainment - sometimes purely for entertainment, sometimes for achievement or reward as well. They can be played alone, in teams, or online; by amateurs or by professionals. The players may have an audience of non-players, such as when people are entertained by watching a chess championship. On the other hand, players in a game may constitute their own audience as they take their turn to play. Often, part of the entertainment for children playing a game is deciding who will be part of their audience and who will be a player. Equipment varies with the game. Board games, Go, Monopoly or backgammon need a board and markers. Card games, such as whist, poker and Bridge have long been played as evening entertainment among friends. For these games, all that is needed is a deck of playing cards. Other games, such as bingo, played with numerous strangers, have been organised to involve the participation of non-players via gambling. Many are geared for children, and can be played outdoors, including hopscotch, hide and seek, or Blind man's bluff. The list of ball games is quite extensive. It includes, for example, croquet, lawn bowling and paintball as well as many sports using various forms of ball. The options cater to a wide range of skill and fitness levels. Physical games can develop agility and competence in motor skills. Number games such as Sudoku and puzzle games like the Rubik's cube can develop mental prowess. Video games, played using a controller to create results on a screen, can also be played online with participants joining in remotely. In the second half of the 20th century and in the
21st century the number of such games increased enormously, providing a wide variety of entertainment to players around the world. They are particularly popular in Korea. The World Chess Championship is played to determine the World Champion in the board game chess. Men and women of any age are eligible to contest this title. The official world championship is generally regarded to have begun in 1886, when the two leading players in Europe and the United States, Wilhelm Steinitz and Johann Zukertort, played a match. From 1886 to 1946, the champion set the terms, requiring any challenger to raise a sizable stake and defeat the champion in a match in order to become the new world champion. From 1948 to 1993, the championship was administered by FIDE, the world chess federation. In 1993, the reigning champion (Garry Kasparov) broke away from FIDE, leading to the creation of two rival championships. This situation remained until 2006, when the title was unified at the World Chess Championship 2006. The current world champion is Viswanathan Anand, who won the World Chess Championship 2007 and successfully defended his title against former world champion Vladimir Kramnik in the World Chess Championship 2008, against Veselin Topalov in the World Chess Championship 2010 and against Boris Gelfand in the World Chess Championship 2012. In addition, there is a separate event for women only, for the title of Women's World Champion, as well as separate competitions and titles for juniors (under 20 years of age), seniors (60+ for men, 50+ for women), and computers. Computers are barred from competing for the open title.